Nexplanon

"Nov. 20, 2012 -- Oral contraceptives should be made available without a prescription to reduce unintended pregnancies, according to a newly published opinion by the American College of Obstetricians and Gynecologists (ACOG).

Figure 20: Mean (± SD) Serum Concentration-Time
Profile of Etonogestrel After Insertion of NEXPLANON During 3 Years of Use

Distribution

The apparent volume of
distribution averages about 201 L. Etonogestrel is approximately 32% bound to
sex hormone binding globulin (SHBG) and 66% bound to albumin in blood.

Metabolism

In vitro data shows that
etonogestrel is metabolized in liver microsomes by the cytochrome P450 3A4
isoenzyme. The biological activity of etonogestrel metabolites is unknown.

Excretion

The elimination half-life of
etonogestrel is approximately 25 hours. Excretion of etonogestrel and its
metabolites, either as free steroid or as conjugates, is mainly in urine and to
a lesser extent in feces. After removal of the implant, etonogestrel
concentrations decreased below sensitivity of the assay by one week.

Clinical Studies

Pregnancy

In clinical trials of up to 3
years duration that involved 923 subjects, 18-40 years of age at entry, and 1756
women-years of use with the non-radiopaque etonogestrel implant (IMPLANON), the
total exposures expressed as 28-day cycle equivalents by study year were:

Year 1: 10,866 cyclesYear 2: 8581 cyclesYear 3: 3442 cycles

The clinical trials excluded
women who:

Weighed more than 130% of their ideal body weight

Were chronically taking medications that induce liver
enzymes

In the subgroup of women, 18-35 years of age at entry, 6
pregnancies during 20,648 cycles of use were reported. Two pregnancies occurred
in each of Years 1, 2, and 3. Each conception was likely to have occurred
shortly before or within 2 weeks after removal of the non-radiopaque
etonogestrel implant. With these 6 pregnancies, the cumulative Pearl Index was 0.38
pregnancies per 100 women-years of use.

Return To Ovulation

In clinical trials with the non-radiopaque etonogestrel
implant (IMPLANON), the etonogestrel levels in blood decreased below
sensitivity of the assay by one week after removal of the implant. In addition,
pregnancies were observed to occur as early as 7 to 14 days after removal.
Therefore, a woman should re-start contraception immediately after removal of
the implant if continued contraceptive protection is desired.

Implant Insertion And Removal Characteristics

Out of 301 insertions of the NEXPLANON implant in a
clinical trial, the mean insertion time (from the removal of the protection cap
of the applicator until retraction of the needle from the arm) was 27.9 ± 29.3
seconds. After insertion, 300 out of 301 (99.7%) NEXPLANON implants were
palpable. The single, non-palpable implant was not inserted according to the
instructions.

For 112 out of 114 (98.2%) subjects in 2 clinical trials
for whom insertion and removal data were available, NEXPLANON implants were
clearly visible with use of two-dimensional x-ray after insertion. The two
implants that were not clearly visible after insertion were clearly visible
with two-dimensional x-ray before removal.

Last reviewed on RxList: 6/13/2014
This monograph has been modified to include the generic and brand name in many instances.